The present invention relates generally to hearing protective earplugs and is more particularly concerned with pre-molded earplugs of the push-in type. Specifically, the present invention relates to a new concept for an insertion stem for push-in type of earplugs that permits easy and deep insertion of the earplug with less pressure and less contact of the stem with the sidewalls of the ear canal. This earplug will fit and provide comfortable sound attenuation to a larger number of individuals than prior art earplugs.
Pre-molded earplugs are composed of different materials. One such material is resilient polymer foam material such as foam rubber, polyurethane or plasticized polyvinylchloride. For example, in U.S. Pat. No. 5,188,123 there is disclosed a push-in type earplug comprising a soft, elastic foam body element having a stiff axially oriented stem by which to facilitate insertion and removal of the body element into and from the ear canal. Another type of push-in earplug includes a central shaft and extending there from at a front end at least a single flange member. These earplugs are generally composed of an injection molded resilient elastomer material such as synthetic rubber material or natural rubber. The flange element extends rearward from the front end of the shaft member and also extends rearward from the front end and is so spaced so as to provide a free annular space between the flange and the shaft. An earplug of this type may be seen in U.S. Pat. No. 5,957,136.
A major problem generally incurred with all of these pre-molded earplugs of the prior art resides in the anatomical fact that the human ear canal is quite variable in size and geometry. Substantially, all ear canal include at least one curved section so that there is not a straight path between the outside of the ear and the inner ear. This is a protective measure in the human ear to prevent a direct path to the inner ear, which could be compromised by a finger or a stick or any other foreign object. As a result, a single type of a pre-molded prior art earplug has not been found capable of accommodating the broad range of human ear canals in both size and geometry. Quite often in inserting the pre-molded earplugs of the prior art, the stem member cannot be manipulated to insert the front end to the proper position to maximize attenuation without incurring discomfort by touching the sidewall of the ear canal thereby irritating the ear canal during use of the earplug.
The great majority of the existing push-in types of earplugs have straight stems generally made out of relatively stiff plastic materials (for instance the earplug described in U.S. Pat. No. 5,188,123). However, to provide proper insertion, the plastic stem of this type of earplug should be flexible/bendable as the human ear canal is not straight and varies among individuals in size and shape. However, to bend a plastic stem inside the ear canal may not be ideal and can increase the pressure and may not be comfortable for the wearer either during insertion or during wear.
In U.S. Pat. No. 3,811,437 and Reissue Pat.No. 29,487, roll down type hearing protective earplugs composed of viscoelastic polymeric foam are shown to be compressed, inserted into the ear canal and therein allowed to expand to result in a comfortable and complete acoustic blocking of the ear canal. This type of earplug does conform to the shape of the ear canal but with current types of stem-mounted earplugs, the stem portion does not. The roll down type of foam earplug possesses certain deficiencies that prevent their use in certain hearing protective situations. This type of earplugs is prepared for insertion by initially rolling it down between thumb and fingers to compress the earplug to below the size of the ear canal into which it is to be inserted. For hygiene reasons, the user's hands should be clean at the time of use. In many noisy industrial environments, abrasive materials or harsh chemicals are present and can become imbedded in the earplug. Since these contaminants may be present on the user's hands, the first step of cleansing the hands can be a bother before using the earplugs. The present invention is directed to a design that will overcome the above deficiencies since the earplug is inserted using a stem member with a handle portion located outside of the ear canal.